Author Topic: Tough Problem To Locate Need Help  (Read 15160 times)

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Offline KE5FX

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Re: Tough Problem To Locate Need Help
« Reply #50 on: April 28, 2016, 07:19:55 pm »
The through hole cap I have is a 50volt 10 uF cap. someone told me that it won't last because of the higher voltage rating. I would have thought it puts less strain on the cap no?

That's a myth.  It'll be fine.
 

Offline Gyro

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Re: Tough Problem To Locate Need Help
« Reply #51 on: April 28, 2016, 07:38:46 pm »
It's got to be worth a try, even if only to confirm (or not) the diagnosis. If you bend the leads right you shouldn't need to tape anything.
Chris

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Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #52 on: April 28, 2016, 07:44:39 pm »
I'm going to give it a try tomorrow. Thanks for all the help. Just never messed with SMD components before, and really don't have the proper tools to do so. If this bandaid works, I'll be happy. I checked the entire deck out for the right record drive, and everything else is still working fine!
 

Offline jitter

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Re: Tough Problem To Locate Need Help
« Reply #53 on: April 28, 2016, 07:59:37 pm »
Yup! Looks like the angled edge is positive, and the black marked edge Negative. Thats what I thought. So the cap must be smoothing the voltage, and the Inductor behind it is smoothing the current? Is it a power supply thing maybe. I don't know I'm just guessing LOL!

In that case, maybe you should get the service manual and find out what it does.
A copy can be found here (wait for the word "...processing..." to change to "Get Manual").

C457 and L441 are on page 75, upper left of IC402. They're on the output of IC410, a 2.7 V voltage regulator.
Thou shalt measure voltages... so, before you go and solder anything parallel, first measure if there's 2.7 V present across the cap, cold and warm.
« Last Edit: April 28, 2016, 08:08:21 pm by jitter »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #54 on: April 28, 2016, 08:04:22 pm »
Yup! Looks like the angled edge is positive, and the black marked edge Negative. Thats what I thought. So the cap must be smoothing the voltage, and the Inductor behind it is smoothing the current? Is it a power supply thing maybe. I don't know I'm just guessing LOL!

In that case, maybe you should get the service manual and find out what it does.
A copy can be found here (wait for the word "...processing..." to change to "Get Manual").

C457 and L441 are on page 75, upper left of IC402. They're on the output of IC410, a 2.7 V voltage regulator.
So, before you go and solder anything parallel, first measure if there's 2.7 V present across the cap, cold and warm.

Good Idea. Thanks! I already put it all back together, because I kinda gave up on it, but I'll give it one more try. I know that the other side of the board has no reaction to the heat, and all I can do is isolate other components with a cardboard tube. soon as I heat up the cap it plays fine. Blast some compressed air on it for just a few seconds, and it immediately drops out. Hope this is it!
« Last Edit: April 28, 2016, 08:07:20 pm by tony3d »
 

Offline jitter

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Re: Tough Problem To Locate Need Help
« Reply #55 on: April 28, 2016, 08:20:23 pm »
Well, after looking a bit more at the schematic, C457 seems to be in the right spot for your symptoms.
The signal from the pickup is first processed by IC403 and its outputs go straight to IC402. The 2.7 V is used all around IC402 (along with 3.3 V).

Yeah, definitely worth checking.
« Last Edit: April 28, 2016, 08:22:32 pm by jitter »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #56 on: April 28, 2016, 08:55:10 pm »
Well, after looking a bit more at the schematic, C457 seems to be in the right spot for your symptoms.
The signal from the pickup is first processed by IC403 and its outputs go straight to IC402. The 2.7 V is used all around IC402 (along with 3.3 V).

Yeah, definitely worth checking.

Yup! Well this will be my first diagnosis LOL! The deck is beautiful other than that, sound fine and works for about 4 minutes when heated. I will definitely try this tomorrow.Never thought of just paralleling a regular electrolytic.
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #57 on: April 29, 2016, 12:18:17 pm »
Well, It's not the cap. I'm getting 2.640 volts cold! I'm afraid this repair will probably be beyond my expertise. Damn so close! I'll leave it opened incase anyone has more ideas.
« Last Edit: April 29, 2016, 12:27:47 pm by tony3d »
 

Online CJay

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Re: Tough Problem To Locate Need Help
« Reply #58 on: April 29, 2016, 01:29:54 pm »
Well, It's not the cap. I'm getting 2.640 volts cold! I'm afraid this repair will probably be beyond my expertise. Damn so close! I'll leave it opened incase anyone has more ideas.

Try it and see if it works.

That 2.64V may have significant ripple, noise or be dipping as the DAC and other circuitry is initialising.

It will only cost you a few pennies to replace the cap.
M0UAW
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #59 on: April 29, 2016, 01:37:52 pm »
Well, It's not the cap. I'm getting 2.640 volts cold! I'm afraid this repair will probably be beyond my expertise. Damn so close! I'll leave it opened incase anyone has more ideas.

Try it and see if it works.

That 2.64V may have significant ripple, noise or be dipping as the DAC and other circuitry is initialising.

It will only cost you a few pennies to replace the cap.
Can I just solder onto this cap? Really don't want to try to remove that SMD with just my soldering station. Trouble is it would be twice the capacitance right? Was going to use a through hole cap.
« Last Edit: April 29, 2016, 01:47:17 pm by tony3d »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #60 on: April 29, 2016, 02:12:53 pm »
Ok, I soldered the negative lead of the through hole to the neg side of the SMD, then while loading a disc touched the pos to the pos of the SMD, and it mounted! first time with no heat! Wish I could get that cap off! really afraid to mess with it. But this does seem to work!
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #61 on: April 29, 2016, 02:23:01 pm »
Well I soldered the pos on, and it works Perfectly! My first lagiamite repair thanks to all your help! You don't know much this means to me, because this deck was the last Christmas present from my brother who passed away 7 years ago. Lot of sentimental value is attached more than anything! Thanks again for all the great help! Learned a lot to! This also helped dissipate my fear of working on a board! Thanks again to all. I'll post pics shortly. Just letting play a while LOL!
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #62 on: April 29, 2016, 02:42:51 pm »
Here it is. Been play for nearly 30 minutes Plugged into my Emotive RSP2 Preamp driving my Crown XTI2000 Power amp! Sounds perfect! no skipping, no audible distortion, Just perfect! Thanks again for all the help!
« Last Edit: April 29, 2016, 05:15:24 pm by tony3d »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #63 on: April 29, 2016, 03:08:29 pm »
Now it dubs from deck to deck with no errors! Use to be when that cap was going bad I couldn't get through one recording without it loosing it's way half way through! Works perfect now!
« Last Edit: April 29, 2016, 05:01:17 pm by tony3d »
 

Offline Gyro

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Re: Tough Problem To Locate Need Help
« Reply #64 on: April 29, 2016, 03:38:14 pm »
Congratulations on the localization and the fix!  :-+
Chris

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Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #65 on: April 29, 2016, 03:56:18 pm »
Congratulations on the localization and the fix!  :-+

Thanks! Could have never done it without all the help! Been playing fine for over an hour!
« Last Edit: April 29, 2016, 04:02:47 pm by tony3d »
 

Offline cvanc

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Re: Tough Problem To Locate Need Help
« Reply #66 on: April 29, 2016, 04:23:38 pm »
Here ya go Tony!  Nice job.

« Last Edit: April 29, 2016, 04:25:53 pm by cvanc »
 

Offline Brumby

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Re: Tough Problem To Locate Need Help
« Reply #67 on: April 29, 2016, 04:25:40 pm »
I'll add my congratulations as well.

You do realise that by tracking the fault zone down with a hair dryer, you had done 75% of the head scratching?  Without that, it would have had a much more challenging exercise.

It's great to see a piece of equipment repaired, especially when it's something special.
 

Online Shock

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Re: Tough Problem To Locate Need Help
« Reply #68 on: April 29, 2016, 04:46:41 pm »
Grats and good work for having a go.
Soldering/Rework: Pace ADS200, Pace MBT350
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Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #69 on: April 29, 2016, 04:52:52 pm »
I'll add my congratulations as well.

You do realise that by tracking the fault zone down with a hair dryer, you had done 75% of the head scratching?  Without that, it would have had a much more challenging exercise.

It's great to see a piece of equipment repaired, especially when it's something special.

I guess, but without the guidance from this forum, and reassurance, I probably would still have a failed component! I've built a bunch of kits, breadboard circuits, and experiment, but never actually fixed something like a hifi component! It feels great, and makes me want to play with other broken stuff LOL! I know electrolytics are always something you should check first, now I believe it! It was tough to do with a hair dryer. I used a toilet paper tube to isolate components around the ones I was heating up. Started at the left side of the board heating, and cooling, and moving to the right. The cap is rather close to a DAC, and was worried it may have been the little wires in the chip. After repeating the process several times I narrowed it down to one little section of the board. I soldered the negative side first, then carefully held the pos side in place while loading a disc. When I saw it worked I finished! Been playing, and recording perfectly! Throughout all this, I also had removed all the ribbon cables, checked their continuity, trimmed them, and re-sat them. Still can't believe it worked. Now that I think of it I wonder if my scope would have shown a lot of ripple? Was the voltage regulator shutting things down?
« Last Edit: April 29, 2016, 05:18:34 pm by tony3d »
 

Offline jitter

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Re: Tough Problem To Locate Need Help
« Reply #70 on: April 29, 2016, 04:53:25 pm »
Good to know you fixed it!
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #71 on: April 29, 2016, 04:59:22 pm »
Makes me want to buy tweezers!
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #72 on: April 29, 2016, 05:02:09 pm »
Here ya go Tony!  Nice job.



Thanks LOL! That's just about how I feel!
 

Offline jitter

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Re: Tough Problem To Locate Need Help
« Reply #73 on: April 29, 2016, 05:16:26 pm »
Now that I think of it I wonder if my scope would have shown a lot of ripple? Was the voltage regulator shutting things down?

I don't think it was a ripple that was the problem as the 2.7 V is derived from a regulated 5 V.
I think it was more like a stability issue caused by too high ESR on a worn out cap, as suggested earlier in this thread.

The voltage regulator wasn't shutting down, but there may have been instability causing IC402 to malfunction.

Edit: I just noticed that the main power supply unit is not a linear job but an SMPS.
The presence of an inductor in the 2.7 V may be there to help block any remaining switching noise (linear regs, i.e. IC410, do not do a good job at filtering out higher frequencies).
Or maybe the noise from IC402 is kept from going back into the 5 V supply by that little inductor.
« Last Edit: April 29, 2016, 05:26:04 pm by jitter »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #74 on: April 29, 2016, 05:22:27 pm »
Thanks for the explanation! I downloaded the service manual, and will follow the circuit. Does that cap filter the step down voltage from the 5 volt supply?
 


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